- Preheat your oven to 425F. 
- Toss the blackberry filling ingredients together until the berries are evenly coated and with your wooden spoon, gently crush the berries just a bit. 
- Spoon the filling into your crust, leaving the liquid behind in your mixing bowl. 
- Cover with additional slitted pie crust, and fork the edges. 
- Brush the egg mixture topping on the top crust and then sprinkle the top with sugar. 
- As always with pies, cover the edges with foil to prevent the lip of the crust from burning, and remove the foil for the last 15 minutes of baking. 
- Bake 35-45 minutes or until crust is golden brown and pie is bubbling through the top crust. 
- Allow the pie to cool before slicing it.